Four-component relativistic density functional calculations of heavy diatomic molecules

Varga, S.; Fricke, B.; Nakamatsu, Hirohide; Mukoyama, Takeshi; Anton, J.; Geschke, D.; Heitmann, Ana P.; Engel, E.; Baştuğ, Turgut

doi:10.1063/1.480934

Cited by 86 publications

(74 citation statements)

References 58 publications

(37 reference statements)

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“…(2) Relativistic DFT generally employs non-relativistic density functionals due to the limited availability of relativistic functionals [120][121][122][123][124][125]. However, computational studies [126][127][128] indicate that the effect of such relativistic corrections is negligible for spectroscopic constants. For core properties, here represented by the extreme case of the contact density, the situation is less clear.…”

Section: Calibration Of Contact Densitiesmentioning

confidence: 99%

Mössbauer spectroscopy for heavy elements: a relativistic benchmark study of mercury

Knecht

Fux

Meer³

et al. 2011

Theor Chem Acc

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The electrostatic contribution to the Mössbauer isomer shift of mercury for the series HgF n (n = 1, 2, 4) with respect to the neutral atom has been investigated in the framework of four-and two-component relativistic theory. Replacing the integration of the electron density over the nuclear volume by the contact density (that is, the electron density at the nucleus) leads to a 10% overestimation of the isomer shift. The systematic nature of this error suggests that it can be incorporated into a correction factor, thus justifying the use of the contact density for the calculation of the Mössbauer isomer shift. The performance of a large selection of density functionals for the calculation of contact densities has been assessed by comparing with finite-field four-component relativistic coupled-cluster with single and double and perturbative triple excitations [CCSD(T)] calculations. For the absolute contact density of the mercury atom, the Density Functional Theory (DFT) calculations are in error by about 0.5%, a result that must be judged against the observation that the change in contact density along the series HgF n (n = 1, 2, 4), relevant for the isomer shift, is on the order of 50 ppm with respect to absolute densities. Contrary to previous studies of the 57 Fe isomer shift (F Neese, Inorg Chim Acta 332:181, 2002), for mercury, DFT is not able to reproduce the trends in the isomer shift provided by reference data, in our case CCSD(T) calculations, notably the non-monotonous decrease in the contact density along the series HgF n (n = 1, 2, 4). Projection analysis shows the expected reduction of the 6s 1/2 population at the mercury center with an increasing number of ligands, but also brings into light an opposing effect, namely the increasing polarization of the 6s 1/2 orbital due to increasing effective charge of the mercury atom, which explains the nonmonotonous behavior of the contact density along the series. The same analysis shows increasing covalent contributions to bonding along the series with the effective charge of the mercury atom reaching a maximum of around ?2 for HgF 4 at the DFT level, far from the formal charge ?4 suggested by the oxidation state of this recently observed species. Whereas the geometries for the linear HgF 2 and square-planar HgF 4 molecules were taken from previous computational studies, we optimized the equilibrium distance of HgF at the four-component Fock-space CCSD/aug-cc-pVQZ level, giving spectroscopic constants r e = 2.007 Å and x e = 513.5 cm -1 .Dedicated to Professor Pekka Pyykkö on the occasion of his 70th birthday and published as part of the Pyykkö Festschrift Issue.Electronic supplementary material The online version of this article

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Section: Calibration Of Contact Densitiesmentioning

confidence: 99%

Mössbauer spectroscopy for heavy elements: a relativistic benchmark study of mercury

Knecht

Fux

Meer³

et al. 2011

Theor Chem Acc

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“…In spite of various theoretical [41][42][43] and experimental [44][45][46][47][48] studies, the molecular properties of Pt 2 are not well known. In particular, the identity of the ground state electronic structure of this molecule is still unresolved, which leads to difficulty in interpreting experimental observations.…”

Section: E Ptmentioning

confidence: 99%

The ab initio model potential method with the spin-free relativistic scheme by eliminating small components Hamiltonian

Motegi

Nakajima

Hirao

et al. 2001

The Journal of Chemical Physics

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A relativistic ab initio model potential ͑AIMP͒ for Pt, Au, and Hg atoms has been developed using a relativistic scheme by eliminating small components ͑RESC͒ in which the 5p, 5d, and 6s electrons are treated explicitly. The quality of new RESC-AIMP has been tested by calculating the spectroscopic properties of the hydrides of these elements using the Hartree-Fock and coupled cluster with singles and doubles ͑CCSD͒ methods. The agreement with reference all-electron RESC calculations is excellent. The RESC-AIMP method is applied successfully in the investigation of the spectroscopic constants of Au 2 and Hg 2 using the CCSD method with a perturbative estimate of the contributions of triples. The ground state of Pt 2 is also determined by RESC-AIMP with the second-order complete active space perturbation method. The results show that scalar relativistic effects on the valence properties are well described by the RESC-AIMP method. The effect on the basis set superposition error on the spectroscopic constants is also examined.

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“…To improve DFT calculations, various theoretical aspects were introduced. To obtain better energy and geometrical results, dynamical and non-dynamic electron correlation was considered by Lee et al, [15] to obtain reliable spectroscopic data relativistic effects for binding energy for heavy metals were introduced by Varga et al, [9] and Grönbeck and Andreoni [10] studied neutral and anion various shapes to Pt 5 using SLDA and BLYP. Their calculations found that 3-D geometries are not favored up to Pt 5 clusters.…”

Section: De-ee0000466 Ballard Materials Products Incmentioning

confidence: 99%

“…[7,8] In particular, platinum nanoparticles, despite their high price, are considered as the catalyst of choice for fuel cell technology due to their excellent catalytic abilities. Therefore, theoretical and computational [9][10][11][12][13][14][15] investigations as well as experimental approaches [16][17][18] have been performed extensively to understand this material. The aim of this research is the maximizing of the benefit from the use of such precious metal and also understand the underpinning fundamentals of the observed properties.…”

Section: Introductionmentioning

confidence: 99%

Final Project Report: Development of Micro-Structural Mitigation Strategies for PEM Fuel Cells: Morphological Simulations and Experimental Approaches

Wessel¹,

Harvey²

2013

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The overall objectives of this project were to improve the understanding of the design space of fuel cell materials and components and to recommend degradation mitigation strategies that facilitate the achievement of the 2020 technical targets. The deliverables from this project to the public, fuel cell community, and DOE are an open-source code fuel cell performance and durability model including a user-guide for dissemination and use within the public domain, and catalyst layer performance and durability correlations with identification of the design spaces relevant to improved durability.The project was led by Ballard Material Products via a direct subcontract to Ballard Power Systems and included critical contributions from the other subcontractors: Georgia Institute of Technology, Los Alamos National Laboratory, Michigan Technical University, Queen's University/University of Calgary, and the University of New Mexico. Ballard's work, which encompassed the development of the performance and degradation models as well as experimental investigation for model validation and the correlation/durability window development, was carried out at Ballard Power Systems' facility in Burnaby, B.C., Canada.Ballard recognizes the significant contribution made by each of the project collaborators and their respective team members. As well, Ballard recognizes the support provided from the DOE project managers, Dr. David Peterson and Kathi Epping Martin, and the project technical advisor, Dr. John Kopasz.The work was funded by the U.S. Department of Energy, Energy Efficiency and Renewable Energy. DE-EE0000466Ballard Material Products Inc. Chapter IPage iii EXECUTIVE SUMMARYThe durability of PEM fuel cells is a primary requirement for large scale commercialization of these power systems in transportation and stationary market applications that target operational lifetimes of 5,000 hours and 40,000 hours by 2015, respectively. Key degradation modes contributing to fuel cell lifetime limitations have been largely associated with the platinum-based cathode catalyst layer. Furthermore, as fuel cells are driven to low cost materials and lower catalyst loadings in order to meet the cost targets for commercialization, the catalyst durability has become even more important. While over the past few years significant progress has been made in identifying the underlying causes of fuel cell degradation and key parameters that greatly influence the degradation rates, many gaps with respect to knowledge of the driving mechanisms still exist; in particular, the acceleration of the mechanisms due to different structural compositions and under different fuel cell conditions remains an area not well understood.The focus of this project was to address catalyst durability by using a dual path approach that coupled an extensive range of experimental analysis and testing with a multi-scale modeling approach. With this, the major technical areas/issues of catalyst and catalyst layer performance and durability that were addressed are:1. Catalyst and ca...

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Four-component relativistic density functional calculations of heavy diatomic molecules

Cited by 86 publications

References 58 publications

Mössbauer spectroscopy for heavy elements: a relativistic benchmark study of mercury

Mössbauer spectroscopy for heavy elements: a relativistic benchmark study of mercury

The ab initio model potential method with the spin-free relativistic scheme by eliminating small components Hamiltonian

Final Project Report: Development of Micro-Structural Mitigation Strategies for PEM Fuel Cells: Morphological Simulations and Experimental Approaches

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